1. Field of the Invention
The present invention relates to an exposure apparatus and an exposure method for exposing a substrate, a device producing method, and a projection optical system.
2. Description of the Related Art
An exposure apparatus, which performs the multiple exposure for the substrate, is known as disclosed, for example, in Japanese Patent Application Laid-open No. 10-214783 in relation to the exposure apparatus to be used in the photolithography steps.
When the multiple exposure is performed, then a plurality of masks are prepared to execute the exposure with each of the masks in some cases, and a plurality of illumination conditions are prepared to execute the exposure under the different illumination conditions with each of the masks in other cases. In such situations, it is necessary to provide the period of time in which the mask is changed and/or the period of time in which the illumination condition or the like is changed. Therefore, the rate of operation of the exposure apparatus may be possibly lowered, and the throughput may be possibly lowered.